Means for frequency multiplication



July 26, 1927. 1,637,283

K. SCHMIDT MEANS FOR FREQUENCY MULTIPLIC'ATION Filed March 9. 1925 Patented my 26, 1927."

UNITED STATES- PATIENT OFFICE.

m1. son-mm,

Application ma larch a, 1925, Serial No.

. My invention relates to an improved meth d of and means for the multiplication of frequencies occurring in alternating electrical phenomena,.and is especially applica- 6 ble in connection with radio transmission.

As is well known ithas become possible in high frequency working to obtain in the simplest manner high multiplication of the initial frequency by means of iron-cored 1 transformers magnetized by an alternating current. Wave lengths of 600 m. have been obtained with an initial wave length of 42 km. according to the initial number of periods. For these long wave lengths the high frequency alternator is,.on account of the constancy and the stability of the oscillations produced by it since a long time superior to vacuum tubes, asa generator for space telegraphy. .In the case, however, of high'multi licationssuch as mentioned in the examp e -70 times the original fre- (agency-very high iron losses take place in t e, transformer itself which considerably reduce the efficiency of the installation, so

that the valve transmitter having a better efliciency than a high frequency alternator is still superior,in the case of shorter waves, to high frequency alternators. The reason for it is that the low initial frequency requires a relatively large transformer in order to give corresponding production in the case of small wave lengths. It follows therefrom thatthe transformer, owing to the high self induction inthe case of small wave len hs or to the high secondary frequency, is raised to a very high tension which leads to difliculties in the insulation of the transformer. My invention, on the one hand, materiall improves the efiiciency of the frequency mu I 40 .tiplication, more particularly in the case of high multiplication, and on the other hand avoids high tension in the rimary transformer and permits the obtaining of an increase of frequency with..-good efliciency up.

1 to 250 m. waves with the initial wave of According to my invention the multiplication is carried out in two steps by means of i two transformers, in..such a manner that only a slight multiplication is effected in the second step. .If for instance the frequency has to be multiplied 85 times, in the first stagethe 17-fold and in the second sta the I T 5-fold frequencycan be produced. Alt ough ffflhe fundamental frequeneyfof the'alternator,

or BEBLIN-SUDENDE, Gamma, assrenoa To 0. Lemma ammuonsauscnarr, or BnaLm-rnmrmnor, GERMANY.

a 8 FOR FREQUENCY HE F LTIPLICATION.

14,259, and in Germany February 15, 1924.

the pro ortions of the transformers and the kind o iron used in them have a great influence to the working of frequency changers I have found that, with the iron obtained in the trade for use in high freqquency transformers frequencies may be changed to a 13- a fold up to a 17 -fold with an eminently good efficiency. Consequently the multiphcation is carried in the, rimary transformer only to nearly the'13- old frequency, and a further multiplication corres ndmg to the desired wave length is carried out in the second transformer.

On the other hand, practical experiments have shown that when using frequency transformers magnetized by an alternating current, the number of higher harmonics increases with the magnitude of the multiplica tion. Sometimes these higher harmonics are developed with so great an amplitude that the well known means for suppressing them by loose coupling the aerial circuit is not sufiicient. Better well known means for suppressing higher harmonics is the use of an intermediate circuit. Such an intermediate a. circuit has, however, a still more unfavorable effect on the efiicienc of the whole installation than loose coupling of the aerial circuit- Its manipulation is complicated, as the intermediate circuit has to be adjusted afresh for each wave, and tuned again.

. In employing my invention an intermediatecircuit may be dispensed with-the method bein based on the factthat in the case of smal multiplications as in the second step according to my invention, as already stated, no higher harmonics worth mentioning are produced. .Thus whenthe 5-fold frequency is produced, practically no higher harmonics will appear. If the frequency were straightaway multiplied eighty-five times by means of one transformer, so many higher harmonics would be produced that they could be eliminated to a certain extent only by means of an intermediate circuit. 1

The two accompanyin drawings are diagrams of connections s OWiL by way of examples two forms embodied in my invention:

Fig. 1 showing the connections of two circuits coupled by a self induction without an iron core, Y i

Fig. 2 showing connections for producing oscillations free from higher harmonics.

According to both figures G is the-high frequency generator which is coupled to the self induction L of the fundamental (natural) frequency circuit. This self induction L is connected in series with the condenser'C and withthe iron-cored fre uency transformer T This circuit is tune in a well known manner to resonate with the generator frequency and according to my system of frequency multiplication this resonance is adjusted to a critical Value to be denoted as critical resonance condition by giving the inductance L a relatively large value. The iron core of the frequency transformer T is dimensioned-to be saturated by a fractional part onl -of the peak value of the current. The se f-induction of the circuit (coil L) is given such a value with respect to the capacity C, that by virtue of the saturation of the core and the corres onding alteration of its magnetic err'nea ilit the tuning of the circuit L C 1 is periodically changed froma condition of resonance (critical resonance) to a condition of nonresonance. The magnetic flux of the core changes suddenly each halfcycle from its gOSltIVB to its. negative saturation value. hort tension peaks periodicall" follow each other at regular intervals whic produce by shock excitation damped wave trains of the natural fr uency of the secondary circuit (e. g. 13-fo d the fundamental frequency). By virtue of the regularly occurring-1mpulses quickly following each other a practically undamped wave is roduced. I

To the self induction 1 is coupled the transformer T this coupling could be effected directly or, which 1s referable, with the interposition of a con enser C The oscillation circuit L 0,, T is then tuned to the same multiplied frequency as in the case of the circuit C T L namely-in such a manner that the critical pointof resonance condition is obtained also in this circuit.

Parallel to the winding of the transformer T is connected another oscillating circuit with the self induction L, and capacity C, which is then tuned to the desired wave.

Accordin to another mode of connection represented y Fig. 2, the primary circuit of the second frequency transformer is directly The re erence numbers. a

time the primary (input) circuit of the second frequenc transformer T including the second trans ormer L12. An antenna A is coupled with the secondary circuit of the second transformer L1: as shown;

The coupling of the frequencymultiply ingcircuitmay be made by instead of an inductance by the-diagram of Fig. 1. I

While I have described my invention in certain preferred embodiments I desire that it be understood that modifications may be made and that no limitations are intended other than may be imposed by the scope of the appended claims.

What I claim is:

1. In a hi h frequency multiplication system of the c aracter described for changing afundamental frequency into a higher frequency comprising in combination an; iron cored frequency multiplication transformer havin its input circuit fed by current of said ndamental frequency, a second frequency multiplication transformer connected in cascade with said first frequency transformer and having a multiplication ratio relatively small with respect tothat of the first frequency transformer.

2. Ina hi h frequency multiplication system of the c aracter described for changing a fundamental frequency into another higher frequenc comprisingin combination an iron-cored re uency transformerhaving its as represented input circuit ed by said fundamental frequency, a second frequency transformer hava capacity also ing a multiplication ratio relatively small with respect to that of the first frequency transformer and means forcoupling the output circuit of the first transformer with said in ut circuit of said second transformer.

11 testimony whereof I have aflixed my signature.

KARL soHinnT. 

